Also among the injured were members of an American military family, an official told CBS News.

"One U.S. service member and his family...were caught up in this tragedy. Due to privacy concerns, we are not releasing the status of their injuries at this time," the Department of Defense said in a statement.

Officials told CBS News they expect the number of American casualties in Brussels will go higher.

Authorities were also searching for the missing. Friends are looking for Americans Sascha and Alexander Pinczowski

Among the missing are two Americans from New York: Sascha and Alexander Pinczowski, siblings who were inside the airport at the time of the bombings and haven't been heard from since, according to Facebook postings from friends.

"Please contact if you have seen them or know about their whereabouts. Please share!!!" wrote Karen Van Suijdam of the Netherlands.

In a Facebook post, Court Empey, a family member of Empey's, wrote that the elder missionaries suffered only minor injuries. He said Empey and Wells' injuries were more severe but that he was expected to be okay.

"[Joseph] will need surgery on a leg wound and does have some shrapnel in his ankles and knee. He has some 2nd degree burns to his hands and head. He has been in contact with us," Court wrote.

According to the LDS Church, the men had been accompanying a fourth missionary who was on her way to a mission assignment in Ohio, and who had already passed through airport security.

"Our prayers are with the families of the deceased and injured, including three of our missionaries who were injured and hospitalized," a statement from the First Presidency of the Church read.

"We also pray for the people of Belgium and France as they continue to deal with the uncertainty and devastation caused by the recent terrorist attacks."